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Dec. V 1a, 192s.

u CF R. L. sTpKELY TELEPHONE EXCHANGE SYSTEM Filed July 14, 1927 2 Sheets-Sheet 1 fiAY A. dram-LY ATTORNEY Dec. 1a, 1928. 1,695,828

r R. L. STOKELY TELEPHONE EXCHANGE SYSTEM Filed July 14, 1927 2 SheetsSheet 2 Patented Dec. 18, 1928.

. UNITED STATES PATENT OFFICE.

RAY L. sroxnnr oa FLORAL rARx, NEW YoRR, ASSIGNOR r0 BELL TELEPHONE LARORA'rORIRs, INCORPORATED, or NEW YORK, N. -Y., A CORPORATION or NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

. ments in message registration on party lines.

According to this invention, a party line subscriber, in order to make a revertive call,

sets a train of switches to seize a revertive ringing device whereupon an'operatoris signaled. The operator listens in and, on hearing the parties converse, manipulates a key register. I

The invention is illustrated in Figs. 1 and 2 of the drawing which disclose an automatic telephone system employing switches of the step-by-step type. Fig. 1 shows a party line, a line finder and first and second selector switches, and an Operators position schematically. Fig. 2 illustrates third selector schematically and also shows a special selector in detail and a revertive ringing machine.

Where some party lines in automatic systems are provided with individual message registers for charging the calls, distinction must be made between revertive calls from these lines and revertive calls from flat rate lines. On a revertive call by aflat rate line the calling party line is extended over line finder F through selectors S, S, S and S to cause the operation of the proper message to the code ringing device S. The calling subscriber then replaces his receiver on the switchhook whereupon the ringing device S applies ringing current to the party line to ring first the called subscribers bell and then the calling subscribers bell. These bells are rung alternately until the called subscriber answers. In case the called subscriber does not answer the calling party may release by again removing his receiver from the switchhook and replacing it. On these calls, however, the apparatus has no way Of distinguishing between-the answer of a called subscriber and the second removal of the receiver by the calling subscriber for the purpose of causing restoration. Accordingly, it has been customary to require a subscriber on a message rate party line to call an operator if he wishes to converse with another party on the same line.

g The present system is arranged sothat the subscriber on a message register party line may make a revertivecall in thesame manher that he makes a direct call, namely, by dialing a code which will extend his line to the ringing machine. As soon as he replaces his receiver on the switchhook after having done this, a signal is given to an operator who merely listens in on the connection and when she hears the parties conversing, she operates a key which reverses thecurrent over the connection to prepare for the operation of the calling subscribers message register.

The switches S, S and S are of the well known two-movement step-by-step type with such modifications as are necessary for the purpose of the present invention. The trunk circuit between the finder F and the first selector S is of a type shown and described in detail in my'copending application Serial No. 205,540, filed July 14;, 1927.

The switch S is a single movement rotary step-by-step switch having a bank of terminals 217.

The ringing device S comprises a rotary step-by-step switch connected to the terminals of the bank 217 in such a way as to cause ringing current of different codes to be sent back over a calling party line.

A detailed description will now be given of the manner in which the system operates Assume that the subscriber at station 101 wishes to converse with the party at station 102 on the same line 100. The initiation of the call causes the line finder F to operate and seize the calling line whereupon the calling subscriber transmits impulses to position the selectors S, S and S to extendthe calling line to the selector switch S When the switch S is seized a circuit is completed from battery, through the right winding of relay 204, right normal contact of relay 200, inner 207. Relay 207 at its left contact grounds the sleeve conductor 224 to hold the extended connection.

The'last series of impulses, delivered to the switch S, causes the successive release and operation of relay 204. On the first re lease of the relaya circuit is closed from ground, through the back contact of said relay, inner right contact of relay 207, normal contacts'of the spring combination 210, winding of slow-release relay 208, winding of the rotarystepping magnet 212 to battery. Relay 208 operates and shifts the stepping cir cuit so that it leads through the armature and front contact and the winding. of said relay. The mzwnet 212 steps the brushes 22.5 50228 lnclusive on the first set of terminals bank 217. For each succeeding impulsethe.

brushes are advanced one set of terminals.

Assume that the last digit i'srepresented by ing the transmission of t e last'iinpulse andv since t 1e relay-207 mai: was its armatures .ft'ollowing (the release of relay 204 a circuit may now llDQztlflCECl from ground, through the back contact. of relay 204 front contact of relay207, back contact of relay 208,"left contact of relay 205, brushes 226and225 and to the grounded sleeve conductor 224.

13116 connected 1' erminals, conductor 229, through the winding of relay 201 to battery. Theugronnded conductor 229 is also extended through the contact and windingo-f relay 203, Gmlductor230, tihnough the switches S S and :S,th1touglr the con-tact and windingof magnet 108 to battery. l he manner in which battery potential is connected to the switch I S is disclosed and described in my copend- 'ing application above mentioned Serial No.

205,540, filed July '14, 1927. Relay 203 operates and looks through its lett'front contact lay 201. also energizes and connects the calling subscribers line to the ringing equiplnent. completes a sulistitute holding circuit tor slowwelay to maintain theconneetion. i 201 also completes a circuit froni batiery, tlmoriglitlie winding of, nelay 213, contact of relay120l, interrupter 216 to ground. Each {time the interruptercloses, relay 21:3 operates and; closes a circuit for the stepping gnagnet 215w-hich-movesthe brushes 218 to 22 2 inclusiuelztrom position to position.

When the switch S reaches; positionfi a circuit is closed. from groundthrongh brush 220, conductor 28,1, contactofc relay 20 1, contact and winding of relay 202 to battery. Relay 2.02 'locksthrough its-winding and front contact, outer ba clr contact .of relay 205 to ground at the front contact of relay 207. In. positions 6 and 9 of the switch s z a circuit is closed; from ground, through the hrush 220, brush 22-8, upper lower contact ofrelay 202, winding of relay 2919- to battery. 7 Relay 209-operates and connects the ringing gen .era to 111a circuit through the i rontcontact switch S V When the relay 205eoiperatesla circuit. is

Relay' 201 atits inner lower contact relay 201, and the back contact of relay 206 to ground. VJh-ile the switch S is in posi .tions 8 and 9, a circuit is closed from ground, through the brush 221, thence over brush 122,7, upper contact of relay202, winding of relay 206 to battery. Relay 206j'operates ancl eyenscs {the connection of the generator and ground. to the tip and ring conductors of thelsine. 'lltusgcl uring'two positions of the switch the bell at one substation is rung ll Vixen :the call-rail par ty answers by removwiugliis receiver the ringing relay 205' oper ates in the well known manner and opens the circuit..foi'relay 201. Relay 205 locks 1n=,a circuit :Eronrbattery, through 1ts' right windwin and contact :to ground atathe contact of relay 207. Relay 205 also unlocks relay 202 'which releases :relays 206. and 20.9; The relay 201 disconnect theringing equipment and reconnects the: relay 204 tothe subscribefs line. Relay 20 1- operatesand recloses the holdingcircuit of relay 207. Relay-201' in releasingopensl the circuit of relay 213 to prevent further stopping of the completed from battery, through the signal lamp .111, right contact I015, relay 203, outer ledft .centnctloqf relay 200,;outer right front contact of relay- 205,-to ground at the front tion Q, observing tlie'lamp 1 11, knows. that a re .ve call is being made. She inserts got-her cordciifcuitinto gack 1109-1111(1 the pantai *s conversing she knows the call has been successfulnnd proceeds to charge the The key completes La circuit from battery, through the sleeve ofsthe jac'i 109,. contacts of said hey, conductor 112, right winding of relay 200 to ground. Relay 200 operates and lockssin a .cin uitztrom battery, through is left winding and outerleft front contact,

Relay 20,0 revenseslt-he direction ofv current flow (through the-windings of relay 204m the .tip and ring conductors or. the line. This reversal ofcurrent causesltghe operation of the polarized relay 106-in the trunk circuit between the finder and the selector S. :Relay 106 in operating closes a circuit for relay 107 i thee nversati n'is over and thesub- 210, winding-of release magnet 211- listens inon the connection Whensheliears 'ca'l ling subscriber by operating-the key 110.

battery. Magnet 211 restores the switch S to normal. Relay, 207 also removes ground from conductor 224 causing the release of switches S S and S and F.

During the release of the trunk circuit between the finder F and theselector S, a circuit is completed from battery, through the contact of relay 107, thence over conductor 113, through the front contact of relay 105, assuming this relay to be operated, through a brush on the finder switch F, and the winding of the messageregister 10 1 to the opposite pole of battery and ground. The register 104 thus operates, charging the call to the subscriber of station 101.

It will be obvious by inspecting the switch S that different codes for signaling the party lines may be selected by setting the switch S on different terminals in its bank 217.

The manner in which a party line is tested to determine which party initiated the call is fully described in the patent to Taggart et al. No. 1,513,351, granted October 28, 1924.

What is claimed is:

1. In a telephone system, a party line, a message register for each party, a revertive ringing machine, selector switches controlled by a subscriber on the party line for seizing said machine when a revert-ive call is made, an operators position, means for signaling the operator if a connection is extended to said machine, and means controlled by the operator for selectively operating said mes sage registers;

2; In a telephone system, a party line, a

message register for each party, a revertive ringing machine, selector switches controlled by a subscriber on the party line for seizing said machine when a revertive call is made, means controlled by said machine for signaling the parties on said line, an operators position, means responsive to the seizure of said machine for signaling the operator, and

means under control of the operator for so lectively operating said registers.

3. In a telephone system, a party line, a message register for each party, a revertive ringing machine, selector switches controlled by a subscriber on the party line for seizing said machine when a revertive call is made, an operators position, means controlled by one of said selectors responsive to the seizure of said machine for signaling the operator, means at said position for listening in on the connection, and means controlled by the operator for actuating said registers.

4. In combination, a party line having in- 'dividual message registers, a revertive Signaling device, automatic switches controlled by the subscribers for extending said line to the signaling device, means controlled by the calling subscribers switchhook for ren dering said signaling'device eflective to sig nal both the calling and called parties, an operators position, means responsive to the seizure of said device for signaling the operator, and means controlled by the operator for actuating said registers.

5. In combination, a party line having individual message registers, a revertive signaling device, automatic switches controlled by the subscribers for extending said line to the signaling device, means controlled by substations on the party line, an operators position, a lamp at said position lighted in response to seizure of the signaling device, and means controlled by the operator for reversing the flow of current over the extended connection to cause operation of one of said registers.

Inwitness whereof, I hereunto subscribe my name this 8 day of July, A. D. 1927.

' RAY L. STOKELY. 

